Plasmonic enhancement and sensing using upconversion nanoparticles

This thesis reports on the photoluminescence modulation of upconversion nanoparticles (UCNPs) using plasmonic nanostructures and fluorescent dyes for applications in bioimaging and sensing. I start by demonstrating plasmonic enhancement of UCNPs using a metal-insulator-metal (MIM) nanostructure. The MIM nanostructure supports a highly localized surface plasmon mode at the absorption wavelength of the UCNPs. The structure can be lifted off the substrate and dispersed into water for bioimaging experiments. UCNP emission is enhanced by over three orders of magnitude when using the MIM nanostructure. As a proof of principle demonstration, the MIMs are successfully used to image cancer cells. Next, I model the effects of Förster resonant energy transfer (FRET) in a dye-conjugated UCNP sensing system. In these systems, sensing can be achieved by the modulation of FRET between the dye and the UCNP. The effects of FRET in such cases are complex as the extent to which FRET is experienced by the rare-earth ions is dependent on their position within the nanoparticle. I develop an analytical model to accurately describe the effects of FRET for such a system. The model is verified using a pH sensor comprised of Fluorescein Isothiocyanate (FITC) and thulium (Tm3+) doped UCNPs. I extend the model to the case of core-shell UCNPs and discuss the design of an optimal FRET-based biosensor using UCNPs. Finally, I propose a novel approach to quantitative sensing of pH using the FITC – Tm3+ UCNP sensing system. I analyze the upconversion mechanism in Tm3+ UCNPs and show that it is possible to design a FRET-based ratiometric sensor where the two wavelengths measured have no overlap with the dye absorption spectrum. This system can be used to realize an ideal quantitative sensor where a calibration curve established in a lab serves as a valid reference for in vivo and in vitro measurements. Sensitivity to pH is demonstrated experimentally and the system is found to be superior to current techniques reported in the literature that use a photon reabsorption-based approach

Radijus utjecaja oborine nad područjem monsuna u Indiji

The paper describes an analysis of rain gauge data to determine an appropriate radius of influence to use for the objective analysis of rainfall over Indian monsoon region. The correlation co-efficient (CC) of rainfall between rain gauges in discrete distance intervals is computed, and the distance at which CC falls to 0.3 is chosen as the radius of rainfall influence. The method is applied for the monthly mean rainfall observations for June, July and August of Indian summer monsoon 2001. The method is also tested for a few case studies in relation to varying geographical and synoptic situations. The study shows that the radius of influence of rainfall over Indian region, in general, is around 200 km, but it has certain day to day variations depending on the prevailing synoptic conditions. The finding of the study is expected to be very useful for the objective analysis of rainfall over Indian region.Ova studija prikazuje analizu mjerenja kišomjernih postaja radi određivanja odgovarajućeg radijusa utjecaja za potrebe objektivne analize oborine nad područjem monsuna u Indiji. Računao se koeficijent korelacije oborine između kišomjernih postaja na diskretnim intervalima te je koeficijent korelacije od 0.3 odabran kao radijus oborinskog utjecaja. Metoda je primijenjena na srednje mjesečne vrijednosti oborine za razdoblje lipanj-kolovoz 2001. tijekom ljetnog monsuna u Indiji. Ova je metoda također testirana na nekoliko odabranih slučajeva zbog variranja geografskih i sinoptičkih situacija. Studija pokazuje da je radijus utjecaja oborine nad područjem monsuna u Indiji općenito oko 200 km, iako postoji određena dnevna varijabilnost koja ovisi o prevladavajućim sinoptičkim uvjetima. Rezultati ove studije korisni su za potrebe objektivne analize oborine nad područjem Indij

Circulation characteristics of a monsoon depression during BOBMEX-99 using high-resolution analysis

The skill and efficiency of a numerical model mostly varies with the quality of initial values, accuracy on parameterization of physical processes and horizontal and vertical resolution of the model. Commonly used low-resolution reanalyses are hardly able to capture the prominent features associated with organized convective processes in a monsoon depression. The objective is to prepare improved high-resolution analysis by the use of MM5 modelling system developed by the Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR). It requires the objective comparison of high and low-resolution analysis datasets in assessing the specific convective features of a monsoon depression. For this purpose, reanalysis datasets of NCAR/NCEP (National Center for Atmospheric Research/National Centers for Environmental Prediction) at a horizontal resolution of 2.5° (latitude/longitude) have been used as first guess in the objective analysis scheme. The additional asynoptic datasets obtained during BOBMEX-99 are utilized within the assimilation process. Cloud Motion Wind (CMW) data of METEOSAT satellite and SSM/I surface wind data are included for the improvement of derived analysis. The multiquadric (MQD) interpolation technique is selected and applied for meteorological objective analysis at a horizontal resolution of 30 km. After a successful inclusion of additional data, the resulting reanalysis is able to produce the structure of convective organization as well as prominent synoptic features associated with monsoon depression. Comparison and error verifications have been done with the help of available upper-air station data. The objective verification reveals the efficiency of the analysis scheme